A man in his 70s with a history of hypertension, hyperlipidemia, chronic obstructive pulmonary disease, and moderate pulmonary hypertension presented with shortness of breath, increased abdominal girth, and bilateral leg swelling. He reported recurrent palpitations that occurred randomly and were often associated with shortness of breath. His medications included aspirin, atorvastatin, amlodipine, tiotropium, and a budesonide-formoterol inhaler. He was admitted with a diagnosis of congestive heart failure. Acute coronary syndrome was ruled out and echocardiography showed a left ventricular ejection fraction of 40% compared with 60% 2 months prior. Cardiac catheterization showed 25% narrowing of the left anterior descending artery and a distally occluded right coronary artery, suspected to be chronic. Diuresis was initiated. During his hospitalization, he developed an episode of tachycardia that was captured on telemetry (Figure 1). An electrocardiogram (ECG) was repeated during a tachycardia episode (Figure 2A).